1. Field of the Invention
The present invention relates to modular jacks and, more particularly, to a modular jack with crosstalk reduced by changing the arrangement and shape of terminals.
2. Description of the Related Art
An electric current flowing in a line or terminal induces by electromagnetic or static coupling another electric current in another line or terminal, producing a crosstalk. The crosstalk interferes with signal transmission or causes noise, and many ideas have been proposed to reduce the crosstalk.
Modular jacks and plugs are widely used for telephone sets or local area networks. A modular plug is connected to a plurality of core wires of a cable used for a telephone set or LAN. A modular jack is provided in equipment and receives the modular plug. When the modular plug is plugged in the modular jack, the terminals of the modular jack are connected to the core wires of the modular plug.
Japanese patent application Kokai Nos. 7-302641, 7-106010, and 8-507648 disclose a variety of means for reducing the crosstalk in the modular jack.
The first and second Japanese patents disclose a modular jack in which some of terminals are modified to reduce overlaps of adjacent terminals to thereby minimize the crosstalk.
The third Japanese patent discloses a similar modular jack, in which the overlaps of adjacent terminals are reduced to minimize the crosstalk, having six long terminals and two short terminals arranged in separate planes so that the long and short terminals do not overlap each other, thereby minimizing the crosstalk.
In the first and second prior art, the crosstalk is not solved completely. The third prior art, which employs the two kinds of terminals to avoid overlaps of adjacent terminals, has the following problems.
The different lengths of terminals make the transmission times of signals different. Individual electric signals should reach the equipment at the same time through the modular plug and jack. As electrical signals are speeded up, the difference in transmission time presents a problem.
When the differently shaped terminals are used, the contact pressures on the modular plug are different for each type of terminals, making the equipment less reliable.